Embodiments of the present invention relate to transmitting electrical power and data, for example in a control system for an underwater (for example subsea) hydrocarbon well facility.
For transmitting electrical power and data, communication on power (COP) systems are known where an analogue data waveform modulates a power waveform at one end and, at another other end, power and data filters are used to separate the power waveform from the data waveform.
For long offset power and data transmission systems (for example tens or hundreds of miles), this method allows for bi-directional transmission of power and data on the same copper wires.
These systems are widely used in control systems for subsea hydrocarbon well facilities.
A known system is illustrated in FIG. 1 and uses hardware analogue filters. These filters are not accurate, they are space intensive and they introduce distortions, noise and power losses. Furthermore, transients on the power source can corrupt the data transmission. More particularly, at a topside end of a long COP line 1 electrical power is supplied by a transformer 2 and a power filter 3 to a combiner 4 where data from a modem 5 and a data filter 6 is combined with the power waveform for transmission via line 1. Also, data received from subsea can be extracted from line 1 via the filter 6 and the modem 5. At the other, subsea end of line 1, electrical power is extracted from a combiner 7 via a power filter 8 and a transformer 9 and data is extracted via a data filter 10 and a modem 11. Also, data can be sent to the topside end via modem 11 and filter 10 for extraction from combiner 4.
As prior art, there may be mentioned U.S. Pat. No. 4,398,178, WO 00/46923, EP-A-2 104 240, GB-A-2 441 811, WO 2004/028064, EP-A-0 463 341, US 2006/079971 and GB-A-2 352 376.
As further prior art, there may be mentioned EP-A-2 620 585 and EP-A-2 621 113 which disclose prior art communication and power systems. EP-A-2 602 941 discloses a time division multiplexed communication on power system. Additionally, unpublished European Patent Application No. 12162210.4 discloses a further communication on power system based on DC data signal modulation.
To overcome the drawbacks associated with such systems, embodiments of the present invention provide both electric power and communication in a control system of a subsea hydrocarbon well facility between topside equipment and subsea remote sensors using either pulse width modulation (PWM) or time division multiplexing (TDM) techniques, to simplify the line signalling and line arbitration methods so that the minimum required power may be delivered to a sensor and its associated communications transmitter.